Hi Romani,
The cover art to the edition of "German War Birds" you posted is by 1930's British artist Howard Leigh, who illustrated many of the "Biggles" books and so on.
"Vigilant" was the pseudonym of Cluad W. Sykes, a prolific British writer and translator of the 1930's. Besides writing the similar "French War Birds" (1937)and the biography "Richthofen, Red Knight of the Air" (1934), he translated a number of very good works by Haupt Heydemarck into English, and did a very nice job of it: "Double-Decker C.666", "Flying Section 17," and "War Flying in Macedonia" (the latter contains some very good tales about Eschwege).
Since he had read and translated so many German works, Sykes was particularly well-suited to write "German War Birds". It's an odd collecyion of tales about some very well-known and some obscure German airmen, still (nonetheless) seen through a British writer's lens. "Early Days, West and East" is a chapter that tells about 1914-15, including storeis about Emil Uzelac, and the next chapter retells the tale of Gunther Plueschow's adventures in the Far East. "Boelcke's Own" is actually a pretty decent history of
Jasta Boelcke. There is the obligatory chapter about MvR, followed by Chapter VI about balloon busters Bormann and von Roeth. There are tales about a German who flew the mail into the besieged Germans in Przemysl, Von Cossel and Windisch's daring exploits behind Russian lines, and Falke and Felmy's exploits in the Middle East. He covers von Schleich, Eschwege, and Flashar's leadership of Jasta 5 on the first day of the Cambrai battle.
All of these are paraphrased from first-hand accounts that can be found in various German anthologies. However, they are a good source of some pretty obscure material. Buy it.